A combined side-channel and transient execution attack scheme on RISC-V processors

The escalating progress of RISC-V processors in both academic and industrial realms has drawn significant attention to its open-source Instruction Set Architecture (ISA) and microarchitecture. Nevertheless, the growing threat of microarchitecture transient execution attacks in recent years has posed a severe challenge to the design of processors. Some studies have proposed that the RISC-V microarchitecture still has some flaws from the perspective of transient execution and pointed out the attack surface, which results in the RISC-V processor being unable to ensure integrated circuit and system security at the microarchitecture level.

In this paper, we systematically examine RISC-V microarchitecture security issues and put forward a combined side-channel and transient execution attack scheme. The proposed attack scheme comprehensively analyzes cache security, timing side-channel attacks, and Physical Memory Protection (PMP) across diverse microarchitectures. Not surprisingly, we discover an unknown transient execution flaw by PMP security analysis. Moreover, we introduce 4 transient execution attack primitives exploiting microarchitectural speculative execution flaws and PMP transient execution to bypass data protection and privilege isolation which allow attackers to illegally access sensitive data on the microarchitectures and break the PMP rule-based memory isolation scheme. Experimental results demonstrate that the attack scheme on 6 real-world RISC-V processors achieves a high level of accuracy, successfully attacking 6 microarchitectures with approximately 97.52%. The scheme completes 1,000 attacks in less 60 s which leaks about 2,500 bits, showcasing an average efficiency improvement of 34.17% over the state-of-the-art tool. The attack can successfully retrieve the cryptographic keys, rendering this attack applicable in practical scenarios. Finally, we propose several countermeasures to defend against the attack. We reported CVE and CNNVD vulnerabilities and both are confirmed by the developers for security’s sake.